So then let's try to bring that back, rather than flying under the radar with adblockers that trick adservers into thinking that they're working. Even if the advertisers are serving malware, two wrongs don't make a right.
I think the ethics of ad blocking is similar to software copyright infringement; it undermines the business model of the company that is offering content. For this reason I don't run an ad blocker.
If you're against proprietary software licenses you shouldn't go and install an unlicensed copy of Windows, you should go download a Linux distribution. Just by using Linux you make yourself counted and you help create a sustainable ecosystem of free software. If no one was willing to pirate Windows, a lot more people would be using Linux on the desktop today.
Similarly if you're against the ad model you should go seek out and contribute to sites that aren't built on an advertising business model (e.g. Wikipedia).
The argument that ad networks serving malware justifies using an ad blocker is to me a bit like saying "Target can't secure their customers' credit cards, so I'm ethically justified in using fake credit cards there".
Disclaimer: I work for and own shares in a company that makes most of its money from advertising revenue.